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| From: Marko_Mäkelä
Date: 1998-09-16
Subject: Re: 256K RAM expansions
|
On Wed, 16 Sep 1998, Richard Atkinson wrote:
> Doesn't that expansion remap A14 and 15, so that any of the 16 16K blocks
> can be in any of the four banks?
Yes, and in the case of the C64 and the C128 that is very handy: you can map any 16k block to be visible to the videochip. I'm not sure if your idea would work so. On the plus/4 it doesn't matter, since the TED has a
16-bit address bus.
The 6821 is only 40 pins, and you can make the expansion software-disablable with it. With the 74xx approach you might need several chips that could take more space than the 6821.
> MMUs are not spare! If I had one, I'd rather keep it in case one in a
> machine died. Commodore chips do seem to be incredibly short-lived.
Well, Jameco used to sell them for about $10. They might also have 8501
processors.
Marko
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